Recording media utilizing beams of high energy density, such as laser beams and the like, are known in the art. In such thermal recording media, the recording layers have high enough optical density to cause a local rise in temperature when they absorb an applied light beam, whereby a chemical or physical change is caused so as to bring about a change in optical characteristics in the locality irradiated with the light beam, thereby resulting in recording of the information.
The recording material of the above-described type have many advantages in that they make it feasible to record a large amount of information in a small area thereof, to write and to read information at a high speed, to have a short access time, to provide records exhibiting excellent keeping quality upon long-range storage, and so on.
In general, recording in such a recording material can be effected by scanning thereon a laser beam which has received amplitude modulation depending on an electric time series signal to which information to be recorded has been converted. In this case, there is the advantage that the recorded image is obtained by real time processing.
Recording layers of the above-described kind (heat mode recording layers) can be obtained by providing on a glass or transparent plastic support a metal of Bi, Sn, In, Te, etc., a semi-metal, a semi-conductor or so on in a thin layer form using an evaporation technique or the like, as described in U.S. Pat. Nos. 4,188,214, 4,291,119, 4,069,487, 4,000,334 and 3,665,483.
In the course of handling and storing these recording materials, it happens that scratches are generated on, or foreign substances like dust adhere to, the recording layer surfaces, which produces adverse effects on the reading of records. For the purpose of obviating this defect, sandwich type (overall adhesion type) or air-sandwich type of information recording materials have been employed (Canadian Pat. No. 1,029,130 and U.S. Pat. No. 4,074,282).
As for the support materials, plastics such as polymethyl methacrylate and the like, though they are superior to other conventional plastics in workability, handling facility, production cost, etc., have problems of liability to scratching and, further, inferiority in dimensional stability and surface properties. Therefore, in view of these problems, glass plate supports are preferable to the plastic ones. However, glass plate supports suffer from the defects that they are inferior in adhesiveness to recording layers, they are easily cracked, they have thermal conductivities greater than plastics by a factor of 10 to lower the sensitivity of a recording layer provided thereon, and their long-range use or storage brings about deterioration of recording characteristics through the migration of ions, such as K.sup.+, Na.sup.+, Ca.sup.2+, Mg.sup.2+, Ba.sup.2+, Al.sup.3+, etc., from the glass support into the recording layer. Further, it has been found that the above described problems can be overcome by undercoating the glass base with a specific polymer, and thus the present invention has been attained.
It has been known in Japanese Patent Application (OPI) No. 138066/82 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application") that a conventional polymer is applied to the surface of a base such as glass or metal, etc., by which transmission of heat in the base is prevented by an adiabatic effect of the polymer layer, to thereby increase sensitivity. However, Japanese Patent Application (OPI) No. 138066/82 contains no disclosure showing recognition of the problem of diffusion of metal ions in the base into the recording layer, with resultant reductions in sensitivity or changes in optical density and defects caused by generation of precipitates, nor any solution to overcome such problems.